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scsteve

sqo success

8 posts in this topic

After a lot of research and studying, I finally figured out the SQO instruction. Here's the problem. I'm using a ML 1000 32 pt. I loaded a program to control Christmas lights. Yes, Christmas lights. I use an external timer to start and stop the program. I noticed that, when I turn off the input. The outputs would stay on. Depending on which position the SQO was in. I tried a re-set instruction. The control re-set to position 0. But, the outputs stayed on. I'm missing something here. What instruction do I need to turn off all outputs?

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How do you trigger the SQO, by timer or hardwire in put? How you trigger the output, by using indirect addressing? Do you mind post your PLC code so that we could take a look.

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I trigger the SQO by an external timer, wired into an input. Then ton timers trigger the position of the SQO. Here's the code. TEST_BAK066.RSS

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So you want all outputs off when you turn off I:0/0? Put this in XIO I:0.0/0 MOV 0 O:0.0

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You could also load zero into the position word of the control registers. test_lights.RSS

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Yes, I want all outputs off, when I turn off I:0/0. Thanks for sharing your knowledge guys. I was thinking I needed a MOV instruction, but, was unsure. Seeing the actual code written into my program, was like turning a light on in my head. I was also thinking, the SQO instruction could be a hazardous thing. I was thinking about inadvertant machine operation, after a power outage, or some kind of disruption in the SQO position. I noticed, when I turned off the power to my ML 1000. And powered it up again, it would resume operation on the position it was on, when power was removed.

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Steve - you have discovered a very important "feature" of the Allen Bradley PLC Family. All Data Table Entries and this includes inputs and outputs are retentive thru power loss. This is in stark contrast to most flavors of Omron and Toshiba PLCs where only the retentive tables hold state with power loss. If you look thru the S2 register you'll find a bit for Power up or Power loss can't recall which. You may find using it helpful.

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Wrote in the code, XIO I:0.0/0 MOV 0 O:0.0 , works great. This is an amazing and helpfull site. I was just wondering. Where does the MOV instruction get the value of 0 from? I guess I'm asking from what file does it come from? Last year I didn't have the SQO instruction figured out. So I used TON timers. All 39 of them. And the OTE instruction. I didn't like it at all. I was limited on the light pattern. And the program looked horrible. A lot of upside down"wedding cakes" LOL. I study the code you guys write. And it looks very professional, neat and eficcient. And easy to navigate through. Nothing beats experience.

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